Spring element for a mattress



FIG. 1 is a partial perspective view of a spring element for a mattress according to our new design;

FIG. 2 is another partial perspective view thereof;

FIG. 3 is another partial perspective view thereof;

FIG. 4 is another partial perspective view thereof; and,

FIG. 5 is another partial perspective view thereof.

In the drawings, the broken lines illustrate environment and form no part of the claimed design. 

CLAIM The ornamental design for a spring element for a mattress, as shown and described. 